APPRAISAL OF THE MASS SPECTROMETRY/MASS SPECTROMETRY OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS USING NEW DATA

While previous studies on the mass spectrometry/ mass spectrometry (MS/MS) of polychlorinated dibenzo-p-dioxins; and dibenzofurans (PCDDs and PCDFs) addressed the need for MS/MS methods, optimum conditions for such analyses, and quantification of PCDDs and PCDFs by using MS/MS methods, conflicting data were reported on the latter two topics leading to disparate conclusions. We present a comprehensive set of data that addresses the collision energy optima (i.e., whether differences exist between the PCDD and PCDF isomers and among the homologs), the linearity and reproducibility of the response of the analyte to an internal standard, and ion abundance ratios essential for compound identification. We discovered that the collision energy optima are not affected by the position or number of chlorine atoms on the molecule and that the collision energy optima are reproducible and span 10-25 eV. We also present data that demonstrate for 17 PCDDs and PCD Fs that the response of the analyte to its isotopically labeled internal standard is linear from 2.5 to 1000 pg/ mu L, that the ion abundance ratios are within 25-30% of the theoretical values, and that routine analyses can be performed on a hybrid instrument for at least 24 h. Comparative analyses of fly ash and sediment extracts indicate that in the absence of interferences, high-resolution mass spectrometry and MS/MS provide similar data. In certain cases where greater selectivity is needed, MS/MS can provide accurate quantitative data.